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Steven,

I'll second Ken's suggestion to watch that Sharpening Made Easy DVD. I watched it after two years of sharpening at our farmers' market and learned how important it was to check the burr all along the ground edge. He had lots of other tips that I have integrated into my system during my third season. I'll watch it again, but first I need to decide on a CBN wheel for my T7.

Curt

Ken,

Once the digital microscope and the K100 sharpness tester arrived, I've been able to take a closer look at whether a 10" CBN 600 grit wheel mounted to my T7 would be a good alternative to the SB250 that I've used for the last three years as I sharpen at our farmers' market. I managed to collect 22 knives to test. 4 of the 22 were identical 12" Victorinox butcher knives and 5 were Victorinox 5" boning knives,  so I could come closer to comparing identical knives. I could do my grinding with three different grits: 600 grit on the CBN, 180 grit using a Razor Sharp paper wheel, and the SB250 trued to the fine grit (whatever that is). During all my grinding I could look at the ground surfaces on the blades with the digital microscope, buff the burr off, look again through the microscope, and then finally test the sharpness. Doing this multiple times made me aware of how many ways I could come to the wrong conclusion.

When I used the digital microscope to examine the ground but unbuffed blades, the 180 grit paper wheel and the SB250 appeared to be very similar and to leave a coarser grit pattern than a blades ground by the Tornado CBN 600. The burrs created by the SB250 and the PW 180 were larger and much easier to detect while grinding. The CBN 600 left such a fine burr that it was hard to decide if a burr had been raised even after long grinding. Once the burr was buffed off in the honing, the 180 paper wheel and the SB250  had larger "teeth" along the edge. Made it slightly easier to cut a grapefruit. I didn't try to test how long blades would stay sharp.

Once deburred and buffed I moved the knives to the K100 sharpness tester. The honed knives took an average of 151 grams to break the test media with the scores ranging from 114 on a PW 180 ground knife to 214 on a knife ground with the CBN 600. All the knives except the 214 one passed my paper and left thumbnail tests. I also used a stopwatch to measure how long it took me to grind the 12" Victorinox butcher knives. The CBN 600 took twice as long to raise a burr, and the CBN 600 also took longer on other comparable knives.

I would have loved to try grinding with the CBN 600 in water, But Ken Rizzo did not think grinding in water was a good idea. Since he had kindly loaned me a new CBN for trail purposes, I didn't want to risk doing any damage to his new wheel. Instead I repackaged it and sent it back. I still really like the potential of a 10" CBN on my T7, but I'm left with the question: what grit would work well in my market sharpening enterprise? Ken only has 10" CBN at 600 grit in stock, but you can order 10" CBN at 400, or 200, but they wouldn't be test wheels. Once you decide, you would have to live with your choice. I do have some time to mull the options; the market starts at the end of May.

Curt

While I wait for my USB microscope to arrive  , I did a little more experimentation with my T7 and the CBN 10" 600 grit Tornado from Woodturners Wonders. I mounted the CBN on my T7 and then put the water trough on. I wasn't planning on adding water to the trough but wanted to see how tight the fit was. I had heard it was a tight fit from an Australian turner. In order to screw the EzyLock nut on, I had to replace the thick Tormek washer that goes between the wheel and the bearing with a very thin washer. Even with the thin washer, the EzyLock just fit; and the CBN was very close to the motor housing. Even worse, I found it very difficult to get the water trough off. It took a lot of twisting and tugging to free the trough. This would not be a good situation for me at the end of a busy market.

When I measured the length of the axle hole in the SB250, it was slightly more than 1-3/4" (1-51/64" to be more precise). The CBN wheel axle hole was 2" long. When I contacted Ken at Woodturners Wonders, he said that the 10" Tornado CBN could be customized so the axle hub would be 1-3/4", but customizing does cost more. The 10" CBN wheels at D-Way are 1-1/2" wide but only come in two coarse grits (80 & 180). I haven't found any other 10" CBN options for the Tormek. I'm leaning toward a customized Tornado if I can settle on a grit.

Ken,

I understood that CBN wheels are more aggressive initially. I didn't know how long it would take to break in a wheel, but I assumed that the 600 CBN wheel would be so aggressive at the start that I would be ordering an 800 or 1000 grit CBN wheel for the upcoming season. Instead the new 600 CBN was less aggressive than my well worn SB250. Once the 600 grit CBN was broken in, sharpening knives would be even slower. We'll see how things go after I pick up some more Habitat knives and continue testing.

I've always sharpened knives grinding into the blade. I also discovered yesterday how much I appreciated the water pooling at the edge of the blade as SB250 is grinding into the knife. The amount of water at the edge acts as guide for how close I am to having having each blade side ground. With the CBN it was just sound and a guess. I'm sure I would adjust over time. I know that Ken at Wood Turners Wonders strongly advises against running the CBN's in water, so I won't try water with the test wheel that he sent.

Wood Turners Wonders do have a wide range of grits that are steps down from 600. Perhaps 500 or 400 would be the best choice for me. Your questions are helping me think through this potential purchase.

Thanks!

Curt

Ken Rizzo from Wood Turners Wonders was kind enough to send me a 600 grit 10" CBN wheel for my T7 to test for sharpening knives. My plan was to try one to see if it would be a good replacement for the SB250 wheels that I've been using for my sharpening business. Each season I wear a 10" SB250 down to 7-1/2" by the time the market ends at X mass. I'm not complaining; each wheel will sharpen 1000+ knives during the season. However, the SB250's do go out of round quickly and require retruing back to a round shape every week and sometimes more. The big plus is that I never have use the grader to coarsen the SB250. I just keep it at the fine grit. I was hoping that a CBN would grind as effectively as the 250 and never go out of round or wear out.
   I picked up 6 dull knives from our local Habitat for Humanity store to run my first test. I ground 3 using my SB250 and ground the other 3 with the 10" CBN. I counted the number of passes for each grind and found that the 10" CBN took more passes to raise a burr and the burr was a little less distinct. It also took a little longer to buff the burrs off. I then used a BESS KN 100 to compare how sharp each knife was after buffing. The knives ground with the CBN averaged in the low 170's while the ones ground with the SB250 averaged 212. Not bat in in either case.
   I always thought that the SB250 trued fine was about 1000 grit. After my test today, I'm wondering if the SB250 isn't closer to 500 grit. I'm now starting to think that it would be better for me to get a 500 grit CBN??
   I plan on going back to Habitat for more test knives (they happily take them back sharpened). I'm also hoping that one of my ex-colleagues who is still teaching will let me use a microscope to take a closer look at the grinds.

Curt

Ken,

I'm curious how you determined that the SG250 at 1000 grit was too inefficient as you ground your two knives. As I'm sure you can guess, I'm asking because I'm trying to determine what grit would be best for a CBN wheel mounted on my T7 for my knife sharpening enterprise.

Curt

Ken,

I set the angle according to the type of knife with the help of the Anglemaster.

Your second question brings up a concern I have about the SB250 stones. Yes I can sharpen every market day for 4 hours without having to change the grit or even resurface the blackstone with the fine grit of the stone grader. However, by the end of the market the stone will be significantly out of round. Knives sharpened at the end of the market on the oval stone do seem to be just as sharp as knives sharpened earlier after the stone has been trued.

When I re true at the end of a day's market, I am losing a lot of stone as I true back to round. I find that a stone will last for a season (June-Dec.), about 1000 knives. I've had 3 SB250 stones over 3 years. They all have gone out of round on a weekly basis, and end up about 7" in diameter by the end of December.

Now I'm ready to replace my current stone, and I'm seriously considering a 10" CBN. Even if a CBN only lasted 2 years, it would save some money and time. But I really like the fine grit on the SB250. Is it really a 1000 grit? Would a 1000 grit CBN wheel work as well as the SB250 does? I've been following the discussion on this strand of the forum with great interest.

I so appreciate hearing the experiences of you and others who have been experimenting with CBN wheels. I'm likely to join you.

Curt

Bob,

I also sharpen knives. For me it's at our small local farmers' market using a T7 with a SB250 stone. I second Ken's suggestion to use knife jigs. I have 7 knife jigs on my cart; and when a customer brings knives, I put each knife in a jig and set the angle. Because I've found that the fine grit on the SB250 does a nice job of bringing the edge back, I never have to change grit on the SB250. I can grind them fairly quickly. On a typical busy summer market session  in our resort town I will sharpen 60-70 knives in four hours. Most customers get their knives back sharpened before they leave the market. You get to the point with knife jigs that you put the knife in the jig, and by eye you can see how much you need to adjust the jig to grind at the correct angle. I always check though; it helps give the customer confidence. If I had a convenient space on my cart, I'd probably add a couple more jigs.

Curt

I usually retrue the stone during the first half hour of our market before customers start bringing knives in. The sound of the truing reminds early customers that I am open for business. Once the stone is true again, I make a very SLOW very LIGHT final pass. Generally I'm set to sharpen at that point; but if the stone still feels rough, I'll lightly dress with the stone grader. I've never experienced any difficulties caused by metal particles. Next Saturday I'll bring a magnet to the market and check periodically for metal particles. What kinds of problems do you think metal particles might cause?

Curt

I've been sharpening knives every Saturday at our local farmers' market using a new SB-250 that I installed this June. Since then I've sharpened 935 knives and a couple dozen pairs of scissors. The SB-250 has worn to a SB-195, and I will probably have enough left to continue until the market ends right after Christmas. I use the knife jigs and sharpen both stainless and non stainless knives. I keep the SB at the 1000 grit stage, and at that grit I've been able to even regrind knives that have nicks. I do have to retrue the SB after every 75 to 100 knives because it starts to go out of round. I keep wondering if I have some flaw in my technique that causes the stone to go out of round, but I'm pleased to be able to sharpen a 1000 +/- knives from one stone.

I'm very interested in Steve's DVD video and his materials. I know after watching the short videos Steve has posted at his website that I would learn a lot, but I'm wandering how long the video is.

Thanks - Curt

I guess it's time to contribute my experience after all my lurking   My knife sharpening experience is limited to just one year at our local farmers' market using a T7. I started with the original grey stone & then moved to the SB in the middle of last summer's market when the original wore down. I quickly found that I didn't have to change grits back and forth with the SB stone. I leave it at the fine grit and that grit handles almost every knife even ones with small nicks that require extra grinding. Staying with the fine grit is faster, and the customer will get more life from the knives because I'm removing less metal. I end up honing the edge with the Razor Sharp paper wheel honing wheel & their honing compound.